I want to add cruise control to my 2003 z4. I know I already have the socket et cetera to plug straight into. My question is, can stalks from any other BMWs be used? Are any of them compatible? Some of them such as the five series look really similar, even down to the plug at the end. The difference is, z4 ones cost £100 and all of the others cost about £20! Does anyone know?